1. Field of the Invention
The present invention relates to an image sensor device or photosensor device used with a facsimile machine, copying machine, or image scanner and the like.
2. Description of the Prior Art
Used for conventionally known read-out systems in color read-out devices such as contact type image sensors is a device whereby a white light is shone onto a manuscript and the reflected light from the manuscript passes through a color filter provided in front of a sensor and enters the sensor, and a device using a light source which emits light in a plurality of differing wave lengths, in which the light rays of different wave lengths are successively directed onto the manuscript and color data is formulated from the light reflected from the manuscript.
In conventional devices of this type, the manufacturing process for the color filter used with the sensor incurs a high cost because the provision of the color filter itself is complicated. In addition, as the resolution of the sensor has been increased from 4 dots/mm to 8 dots/mm to 16 dots/mm, the sensor itself has been reduced in size. Accompanying this trend, the size of the color filter has been reduced, so that the higher technological level of the manufacturing process for the color filter has necessitated a higher cost.
Also, problem areas have developed with the method whereby light is emitted in a plurality of successive, differing wave lengths, inasmuch as the read-out device has increased in size and the time necessary for read out has lengthened.
Specifically, in a conventional method for reading the electrical signal for the sensor, the electric signal from a photoelectric converter section is stored in a charge storage means, and this stored charge is read out in succession as an output data.
In order that color is read out in a sensor having a formation of n dots, a red light source is first directed onto the manuscript to read out the stored electric charges in succession beginning with the first dot through the reflected light. When the read out of the n dots is completed, with the red light source, the electric charge stored in the first dot is reset, light from a green light source is emitted, and the stored charge of the first dot is read out within a set time period. Then, the second dot is reset and the stored charge of the second dot is read out within a set time period. This action is repeated n times, then light from a blue light source is emitted, and once again the same action is repeated to complete the read-out of one line.
In the process mentioned above, time is required for 3 n repetitions, so that the time used for read-out becomes extremely long.